McClellen vs. Lee
Union Confederate
Maj. Gen. George B. McClellan Brig. Gen. Robert E. Lee
Brig. General Fitz John Porter
Strength
34,214 57,018
Losses
6,837 7,993
Some of the losses.


Maj. General Fitz-John Porter
Porter was a Brigadier General at the time of the battle.
General George McClellan USA faced the newly appointed General Robert E. Lee CSA at Beaver Dam Creek, stood off Lee’s repeated attacks and with Richmond in sight and victory at hand, Little Mac ordered his army to retreat. Lee wanted to smash the Army of the Potomac while it was exposed and vulnerable. McClellan assigned Brig Gen Fitz-John Porter to cover the retreat. Porter took up a position on the banks over Boatswains Creek near Gains Mill and waited for Lee’s assault.
Porter had 34,000 men and plenty of artillery; he arranged his forces in three lines. The first was along the base of the ridge, the second right behind it and the third, consisting of the artillery, along the top. Against this very strong position Lee hurled 57,000 men.
Lee’s forces had been slow at getting into position and were not able to launch the first of their attacks until early in the afternoon on June 27. Lee’s men were cut down as they tried to ford the creek under heavy fire. Porter repeatedly drove the Confederates back with heavy losses buying time for the rest of the Union Army to fall back to Glendale. Porter’s position finally collapsed at sunset.
There was no fancy footwork at Gains Mill. Porter took a strong position and Lee attacked it head on. Controversy surronds the actions or lack there of by Stonewall Jackson, but that's all. Jackson seemed to be sleepwalking through the whole of the Seven Days Campaign. Jackson, who's men were called the foot cavalry for their marching ablity, never seemed to get where they were supposed to be on time or even in time to effect the outcome of the various battles. I have never seen a good explanation for what Jackson was doing, some Confederate comanders at the time thought that had Jackson supported the attacks at Gains Mill they would have overwhelmed Porter on the first assult.
As it was, the final Union defeat was not a rout. Porter withdrew across the Chichahominy and would again make his presence known at Malvern Hill. Porter's force had suffered nearly 6,000 casualties but had inflicted nearly 9,000 casualties on Lee’s men according to the National Parks Service.
Costly as it was, Gains Mill was Lee's first victory as the general of the Army of Virginia.

Porter's Position over the creek.

Porter's Right.



Looking off to Porter's Left.




Views of Boatswains Creek. The Confederates attacked across this creek.









The Union dug rifle pits on the banks over the creek. The rifle pits formed Porters first line.





Porter's line stretched out along the ridge.
The Union line stretched out further but the field in the photo is private property.

The Union line stretched back along the ridge past the house.

The Confederate view of Porter's position.